21001202220221 has 4 divisors (see below), whose sum is σ = 21001715775612. Its totient is φ = 21000688664832.

The previous prime is 21001202220203. The next prime is 21001202220253. The reversal of 21001202220221 is 12202220210012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15821413132996 + 5179789087225 = 3977614^2 + 2275915^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001202220221 - 2¹⁴ = 21001202203837 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21001202220221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001202225221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 256716350 + ... + 256798143.

It is an arithmetic number, because the mean of its divisors is an integer number (5250428943903).

Almost surely, 2^{21001202220221} is an apocalyptic number.

It is an amenable number.

21001202220221 is a deficient number, since it is larger than the sum of its proper divisors (513555391).

21001202220221 is an equidigital number, since it uses as much as digits as its factorization.

21001202220221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 513555390.

The product of its (nonzero) digits is 128, while the sum is 17.

Adding to 21001202220221 its reverse (12202220210012), we get a palindrome (33203422430233).

The spelling of 21001202220221 in words is "twenty-one trillion, one billion, two hundred two million, two hundred twenty thousand, two hundred twenty-one".